textproduct: Rapid City

KEY MESSAGES

- Severe thunderstorm threat returns Monday across northeast WY, the Black Hills, and southwest SD.

- Cooler temperatures through Tuesday, then a gradual warm up for the rest of next week.

UPDATE

Issued at 1047 PM MDT Sun Jun 21 2026

Main focus with this evening's forecast update was to massage PoPs/QPF/ProbThunder for Monday into Monday evening as NBM didn't always reflect the flavor of higher-res guidance and the CAMs, and take another look at Monday's severe weather potential. Plentiful deep-layer wind shear of 45-60kts and sufficient CAPE/moisture will support a solid supercell regime with at least isolated cell development expected to begin across our northeast Wyoming counties around 1-2 PM per good HREF member consensus. Modest overall CAPE may remain at or below 1,500 J/kg in many areas which also keeps the CAPE profile fairly modest/skinny in the mid-levels of forecast soundings, and this MAY take the edge off the potential for VERY large hail. However, the supercell storm mode with ample shear will still support large hail as a primary threat, with damaging winds over 60 MPH and a non-zero risk of a tornado also on the table. The strongest storms will tend to translate east-southeast across northeast Wyoming, the Black Hills corridor, and southwestern South Dakota over the afternoon and evening, while severe weather potential may drop off a bit east and north of the Black Hills corridor due to slightly lower instability and more of a cap. Definitely stay weather-aware tomorrow!

DISCUSSION

(This Afternoon Through Saturday) Issued at 1043 AM MDT Sun Jun 21 2026

Current upper-air analysis and water vapor imagery depict zonal flow over much of the CONUS with a shortwave positioned over the Dakotas and a surface low over southern AB/SK. Satellite imagery indicates a very moisture-rich air mass over much of SD with dense cloud cover and fog along the eastern Black Hills foothills, however, cloud cover is dissipating over southwestern SD. Radar returns show showers and thunderstorms continue to push east/southeast across northwest, central, and south-central SD. Surface observations show temperatures mainly in the upper 50s to mid 60s, with dew points in the low 50s across northeast WY and mid to upper 50s across western SD. Winds are generally easterly at 10 to 18kts gusting to 26kts across northwest/west-central SD, while winds are northwest at 10kts gusting 18kts. Gusty northwest winds up to 35kts will be possible over northwestern and southwestern SD as the low associated with the shortwave continues to move east.

QPF totals through this morning have varied greatly with some areas receiving over 1", mainly parts of northwestern and south-central SD, while areas around the Black Hills and Rapid City area received less than 0.10". It is still feast or famine when it comes to receiving meaningful precipitation over the region.

Thunderstorms and showers will continue to move through the region today as the shortwave continues to move across the region. Severe weather is unlikely today due to the environment needing to recharge after yesterday's storms. The likelihood of receiving at least another 0.25" of precipitation through the remainder of today into tomorrow morning is highest over central SD where there is a ~40 to 55% chance (12z HREF), with locally higher amounts possible with any heavier showers. There is still a chance that the northern and central Black Hills could pick up at least an additional 0.10" (~35 to 45% chance, 12z HREF), however, it will be isolated to where showers move into the Black Hills and won't be wide-spread. Temperatures will be cooler today with highs ranging in the 60s to low 70s.

This coming week will start off cooler and wet as a cold front pushes through, bringing another round of showers and thunderstorms to the region. SPC currently has a slight risk issued for severe thunderstorms for most of northeast WY, the Black Hills, and far southwestern SD. The environment will potentially support a few supercells capable of producing +1" hail and +60 mph wind gusts. The 12z run of the HREF suggests mean surface-based CAPE, 0-6km wind shear, and lapse rates will be comparable to Saturday, however, frontogenesis may help organize a few stronger storms. Confidence will increase with subsequent model runs.

Unsettled weather is expected to continue throughout the rest of the week, with precipitation chances possible on most days. Temperatures will gradually warm up through the rest of the week.

AVIATION

(For the 12Z TAFS Through 12Z Tuesday Morning) Issued At 509 AM MDT Mon Jun 22 2026

Improvement in flight conditions are expected this morning. However, MVFR CIGS could linger across parts of the western SD plains. Another round of thunderstorms are expected this afternoon and evening, esp over NE WY. TS chances will continue overnight into Tue morning. In addition, widespread MVFR-IFR cigs are expected behind a cool front as it sags into the region late tonight.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.